For a portion to enhance the energy efficiency of an air compressor for general industry, an oil injected type and a water injected type that mix oil or water with air sucked inside a air end and compress them together are known.
The oil or the water has effect that inside leakage is reduced because it seals narrow clearance via which compression chamber connects with another space and effect that the heat of compression is absorbed and the thermic deformation of members of the compressor is prevented, reducing compressing power, and both effects enhance the energy efficiency. The oil injected type excels in reliability because the type has many achievements, however, as a component of oil remains in supplied discharged air though the component is slight, the oil injected type is often not used for application that does not allow even the existence of the minute oil component to food and a semiconductor.
The prevalence of the water injected type has been retarded, compared with the oil injected type because countermeasures against rust, corrosion, the failure of lubrication and others are required, compared with oil because of characteristics of water though no oil content is mixed in supplied air as to the water injected type. However, the development of a water injected air compressor has been recently active because of a request of a market for clean air that includes no oil content and for example, Japanese Patent Application Laid-Open Publication No. 2009-180099 is disclosed.
The adoption of a water injected scroll air compressor is disclosed in Japanese Patent Application Laid-Open Publication No. H8-128395 and Japanese Patent Application Laid-Open Publication No. 2002-89447. Besides, results of experiments in which the efficiency is enhanced by injecting water into the scroll air compressor are described in “Performance of oil-free scroll-type air compressors” written by T. Yanagisawa, M. Fukuta, and Y. Oqi (Shizuoka University) in Proceedings of International Conference on Compressors and Their Systems as an identification number of IMechE 1999 C542/088, issued in September 1999 and published by Institution of Mechanical Engineers (IMechE).